CaImAn an open source tool for scalable calcium imaging data analysis

Advances in fluorescence microscopy enable monitoring larger brain areas in-vivo with finer time resolution. The resulting data rates require reproducible analysis pipelines that are reliable, fully automated, and scalable to datasets generated over the course of months. We present CaImAn, an open-source library for calcium imaging data analysis. CaImAn provides automatic and scalable methods to address problems common to pre-processing, including motion correction, neural activity identification, and registration across different sessions of data collection. It does this while requiring minimal user intervention, with good scalability on computers ranging from laptops to high-performance computing clusters. CaImAn is suitable for two-photon and one-photon imaging, and also enables real-time analysis on streaming data. To benchmark the performance of CaImAn we collected and combined a corpus of manual annotations from multiple labelers on nine mouse two-photon datasets. We demonstrate that CaImAn achieves near-human performance in detecting locations of active neurons

Selective Reduction of AMPA Currents onto Hippocampal Interneurons Impairs Network Oscillatory Activity

Reduction of excitatory currents onto GABAergic interneurons in the forebrain results in impaired spatial working memory and altered oscillatory network patterns in the hippocampus. Whether this phenotype is caused by an alteration in hippocampal interneurons is not known because most studies employed genetic manipulations affecting several brain regions. Here we performed viral injections in genetically modified mice to ablate the GluA4 subunit of the AMPA receptor in the hippocampus (GluA4HC−/− mice), thereby selectively reducing AMPA receptor-mediated currents onto a subgroup of hippocampal interneurons expressing GluA4. This regionally selective manipulation led to a strong spatial working memory deficit while leaving reference memory unaffected. Ripples (125–250 Hz) in the CA1 region of GluA4HC−/− mice had larger amplitude, slower frequency and reduced rate of occurrence. These changes were associated with an increased firing rate of pyramidal cells during ripples. The spatial selectivity of hippocampal pyramidal cells was comparable to that of controls in many respects when assessed during open field exploration and zigzag maze running. However, GluA4 ablation caused altered modulation of firing rate by theta oscillations in both interneurons and pyramidal cells. Moreover, the correlation between the theta firing phase of pyramidal cells and position was weaker in GluA4HC−/− mice. These results establish the involvement of AMPA receptor-mediated currents onto hippocampal interneurons for ripples and theta oscillations, and highlight potential cellular and network alterations that could account for the altered working memory performance

Robots that imagine – can hippocampal replay be utilized for robotic mnemonics?

Neurophysiological studies on hippocampal replay, which was a phenomenon first shown in rodents as the reactivation of previously active hippocampal cells, has shown it to be potentially important for mnemonic functions such as memory consolidation/recall, learning and planning. Since its discovery, a small number of neuronal models have been developed to attempt to describe the workings of this phenomenon. But it may be possible to utilize hippocampal replay to help solve some of the difficult challenges that face robotic cognition, learning and memory, and/or be used for the development of biomimetic robotics. Here we review these models in the hope of learning their workings, and see that their neural network structures may be integrated into current neural network based algorithms for robotic spatial memory, and perhaps are particularly suited for reinforcement learning paradigms

On the Track of the Books Scribes, Libraries and Textual Transmission

Aims and Scope This book offers the hint for a new reflection on ancient textual transmission and editorial practices in Antiquity.In the first section, it retraces the first steps of the process of ancient writing and editing. The reader will discover how the book is both a material object and a metaphorical personification, material or immaterial. The second section will focus on corpora of Greek texts, their formation, and their paratextual apparatus. Readers will explore various issues dealing with the mechanisms that are at the basis of the assembling of ancient Greek texts, but great attention will also be given to the role of ancient scholarly work. The third section shows how texts have two levels of authorship: the author of the text, and the scribe who copies the text. The scribe is not a medium, but plays a crucial role in changing the text. This section will focus on the protagonists of some interesting cases of textual transmission, but also on the books they manufactured or kept in the libraries, and on the words they engraved on stones. Therefore, the fresh voices of the contributors of this book, offer new perspectives on established research fields dealing with textual criticism

Breakdown of spatial coding and interneuron synchronization in epileptic mice

Temporal lobe epilepsy causes severe cognitive deficits, but the circuit mechanisms remain unknown. Interneuron death and reorganization during epileptogenesis may disrupt the synchrony of hippocampal inhibition. To test this, we simultaneously recorded from the CA1 and dentate gyrus in pilocarpine-treated epileptic mice with silicon probes during head-fixed virtual navigation. We found desynchronized interneuron firing between the CA1 and dentate gyrus in epileptic mice. Since hippocampal interneurons control information processing, we tested whether CA1 spatial coding was altered in this desynchronized circuit, using a novel wire-free miniscope. We found that CA1 place cells in epileptic mice were unstable and completely remapped across a week. This spatial instability emerged around 6 weeks after status epilepticus, well after the onset of chronic seizures and interneuron death. Finally, CA1 network modeling showed that desynchronized inputs can impair the precision and stability of CA1 place cells. Together, these results demonstrate that temporally precise intrahippocampal communication is critical for spatial processing